runner duck with shaky legs. any ideas?

One of my 5 week old runner ducks legs are pretty shaky at times. The legs don't shake all of the time but sometimes when the group is all standing around the one's legs just shake. It looks like it is shivering but I'm in Florida and its not cold out. Any ideas as to what could be causing this?

This particular duck does seem to lay down more often than the rest but is not always lying down, just tends to plop down first. She (I think) keeps up with the rest, swims, eats etc. I have been adding Niacin to their water since their arrival. They are eating TSC chick/duck starter/grower 20% protein. I just started mixing their current food with grower/finisher to get a 17% protein mix as suggested by Metzer.

Should I be concerned about the shaking? It is not constant just seems to occur at times.

Its pretty copmmon with many of my runner babies. It seem to happen more often between 3-5 weeks old. Not all of them do it- and it seems to co-incide with growth spurts they go through. It doesnt last more than a a few days to a week. They just seem a little shakey- no other symptoms, but do grow out of it.

We also have one duck out of my runners that had shaky legs for a couple months. he had them almost constantly, and also layed down alot, and we were giving niacin. At katharndid' advice, we gave it again after we had stopped. they finally no longer shake at 3 months old. He is my daughter's FAVORITE duck, he's named Lucky. he is the cutest funniest duck ever lol. it was adorable when his legs shook too.

One of my runner boys was like this too, really wobbly on his legs and sat down a lot. It seemed that his hips were positioned a little bit more forward in his body than the others and his centre of gravity was in a different place which he couldn't quite find, hence the appearance of being off balance all the time. He had had niacin added to his feed from the first week.

Anyway, long story short, he simply grew out of it by about 3 and a half months old. He is now the tallest and most elegant of my runners, completely steady on his feet, and a sweetie! I just made sure that he had a good diet, free ranging with plenty of grass to graze, slugs and mealworms as treats and a bit of "poultry spice" when he moulted. give your duck some time and I am sure time will improve things, so long as you are feeding the right things.